U.S. Pat. Nos. 5,287,731 and 5,401,661 to Florkowski et al. disclose thermo-oxidation engine oil simulation testing. In general, such testing mimics engine and turbocharger conditions in use at that time—for example, by maintaining test device reservoir oil at 95° C. and repeatedly flowing the oil over a test rod heated over a number of half hour cycles, each beginning at 150° C. (held one minute) then to 500° C. (held two minutes) and back to 150° C. (held twenty-four minutes)—with the test oil having an adversely affecting gas such as moist air and/or nitrous oxide pumped from the reservoir, up through a tube containing the heated test rod on which deposits form.
U.S. patent application Ser. No. 09/059,132 by Selby et al. discloses a device for measuring heat transmissibility of oil. In general, that device has a plurality of opposing thermocouples in a deposit formation assembly as in apparatus of the '731 and '661 patents to Florkowski et al.
The foregoing art employs flow from bottom to top, with 100-mL test sample sizes or larger. A commercial embodiment from that can be found as TEOST® apparatus, available from Tannas Company, Midland, Mich., further designated as “33C.” Testing with TEOST® 33C apparatus is considered a bulk oil technique in simulation of conditions found in the turbocharger bearing area of an internal combustion engine. In commonly encountered practice, the reactor sump (reservoir pot) is held at 100° C. to form precursors at high-normal operating conditions; and cyclic heating of the deposit-inducing zone is carried out from 200° C. to 480° C. at designated intervals, say, every 9.5 minutes over 2½ hours or so, for example, over a 114-minute total test time, to simulate turbocharger deposit-forming conditions. A typical run may employ a ferric naphthanate catalyst and a 116-mL or so test sample. Compare, ASTM D6335.
U.S. patent application Ser. No. 08/995,720 by Selby et al. discloses a thermo-oxidation engine oil test apparatus and method. In general, such apparatus and method addresses milder conditions than turbocharger conditions, say, about from 100° C. to 200° C., with, however, test oil including adversely affecting gas such as moist air and/or nitrous oxide also being pumped from a reservoir, also in bulk flow, up through a tube containing a heated rod, on which deposits form.
U.S. Pat. No. 6,365,413 B1 to Hall et al. discloses a thin film thermal oxidative deposit testing device and method. In general, such testing employs a thin film of test oil that, within an enclosing tube, flows downward from an upper part of a central portion of a depositor surface, for example, a rod with a more narrow central portion having a helical wire wrapped around thereabout—noting in addition U.S. Pat. No. D448,689 S to Selby, which discloses a depositor rod for a thin film oxidative oil deposit testing device and method especially at moderately high temperature—with an adversely affecting gas such as moist air and/or nitrous oxide entering about a midpoint of the central portion. A reservoir pot may be avoided. Temperatures can be about from 200° C. to 400° C., with smaller sample sizes, say, about 8.5 mL, employed.
Commercial embodiments from the '413 patent may be found as TEOST® MHT® apparatus, also available from the Tannas Company. Testing with TEOST® MHT® apparatus is considered to be moderately high temperature testing of engine oil for evaluation of its performance correlated with the piston ring belt area of the engine, with the apparatus having a small, unheated storage volume that delivers a liquid sample to a single, thin-film heating zone with a wire-wound depositor rod held at 285° C. for twenty-four hours; a special bulbous clear glass mantle is provided for viewing of the depositor test area during testing; and volatized material can be separated and collected in a special adjunct vessel so that it may be further analyzed and investigated. Typically, a ferric naphthanate catalyst is employed with a 9.6-mL or so test sample. Compare, ASTM D7097.
As excellent as they are, however, and they excel indeed, the aforementioned bench testing apparatus and methodology are not without drawback or limitation, notably in light of the ever changing engine designs and formulations for engine oils, which would demand ever-more particular apparatus and methodology for accurate, precise, and reliable characterizations of their properties so that better, more efficient, and more reliable assessments and predictions can be made concerning their performance in the field. In particular, modern low viscosity oils, which can provide for better fuel efficiency and longer engine life, among other things, more and more contain chelated molybdenum compounds as additives, and these present special difficulties from deposits that can form, which are increased in number and varied in character. Moreover, modern internal combustion engines are designed to operate with lower turbocharger area temperatures than in former years, the modern engines typically operating between about 200° C. and 330° C. or so. Various samples of such modern oils may pass ASTM D6335 testing with TEOST® 33C apparatus, yet be proven to be a failing oil from automotive manufacturers' dynamometer turbocharger test assessments, and vice versa. The other historic TEOST® deposit test, i.e., ASTM D7097 testing with TEOST® MHT® apparatus, as mentioned above, is a ring belt deposit test, which was correlated with piston belt deposits of the Peugeot TU3MH engine test in contrast to the TEOST® 33C test that was correlated with both field oil and dynamometer turbocharger engine test data focusing on turbocharger galley bearing failure (at much higher temperatures that those of modern turbochargers). Although these two historic TEOST® tests do not correlate with each other, they were never intended to do so.
It would be desirable to ameliorate if not overcome one or more of the difficulties, drawbacks, and limitations of the prior art, and to improve the art. In particular, it would be desirable to provide more reliable test apparatus and methodology for testing engine oils for deposits under modern turbocharger conditions, notably to include modern engine oils with their additive packages, which may contain chelated molybdenum and/or other additive(s), and even extending to more advanced formulations, and the like. It would be desirable to provide the art an alternative.